Kilauea Volcano's Deadliest Eruption Revealed

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A band of ancient warriors were en route to battle near the
summit of Mount Kilauea more than 200 years ago when Pele, the
Hawaiian goddess that lives inside the volcano, got angry. Very
angry.

Searing rocks exploded from
Kilauea's summit crater and a thick current of
lava surged toward the warriors, propelled by hurricane-force
winds. More than 400 people died, according to historical
estimates, in the deadliest volcanic eruption in what is now the
United States.

"There have been more powerful eruptions here, but none more
deadly," said Don Swanson, a geologist with the Hawaiian Volcano
Observatory.

Kilauea's legendary eruption happened in November 1790, but until
now the deadly surge of lava associated with it had yet to be
identified, Swanson said during a news conference today (Dec. 6)
at the annual meeting of the American Geophysical Union in San
Francisco.

"We think that we've identified the very eruption, by its
deposit, that was responsible for the deaths of so many people,"
Swanson said. And this eruption points to a more explosive past
for Kilauea than thought. [ History's
Most Destructive Volcanoes ]

Fieldwork also turned up footprints in the muddy ash not far from
the Hawaiian observatory, Swanson said.

"One wonders if those footprints were the last that that person
took," Swanson said.

By carbon-dating explosive deposits and lava flows, Swanson built
an eye-opening timeline of the volcano's history. Advancements in
radiocarbon dating, along with dogged fieldwork, allowed Swanson
to date tiny pieces of carbon, a task that wasn't possible just a
few years ago

"He's found many, many more explosions than we thought existed,"
said Ken Hon, a volcanologist at the University of Hawaii at
Hilo.

Violent eruptions are not synonymous with Kilauea. Its name means
"spewing" or "much spreading" in Hawaiian and the volcano has
been continually oozing out lava since Jan. 3, 1983. People often
walk near these sluggish
rivers of lava that flow down the mountain's slopes and into
the ocean. These "gentle eruptions" are rarely a threat unless
people are doing something foolish, Swanson said, but that hasn't
always been the case.

Over the past 2,500 years, Kilauea has existed on the opposite
end of its eruptive spectrum — in an explosive period — about 60
percent of the time, according to Swanson's new data.

"The major finding that we have is that these are not infrequent
events," Swanson said.

Explosive again?

Kilauea is currently in a lava flow mode, as it has been for the
other 40 percent of the past 2,500 years. During these quieter
periods, the volcano begins to rebuild itself by piling lava flow
on top of lava flow. Kilauea, however, could switch back to an
explosive period without much warning, Swanson said, because
scientists don't fully understand how these explosions begin.
These powerful and
dangerous volcanic periods can last hundreds of years.

"We don't know when the next period of explosive activity may
start," Swanson said. "Is it a threat today? I think the
answer is clearly yes," Swanson said.

Whenever Kilauea returns to an explosive mode, a long-term
evacuation of the summit, a popular vacation spot, will be
necessary.

You can follow OurAmazingPlanet staff writer Brett Israel on
Twitter: @btisrael.Follow
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